From: Jerome Glisse <jglisse@redhat.com>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>,
Linux-MM <linux-mm@kvack.org>,
linux-kernel@vger.kernel.org, John Hubbard <jhubbard@nvidia.com>,
Ira Weiny <ira.weiny@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
Balbir Singh <bsingharora@gmail.com>,
Dan Carpenter <dan.carpenter@oracle.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister()
Date: Sun, 12 May 2019 11:07:24 -0400 [thread overview]
Message-ID: <20190512150724.GA4238@redhat.com> (raw)
In-Reply-To: <fa2078fd-3ec7-5503-94d7-c4d1a766029a@nvidia.com>
On Tue, May 07, 2019 at 11:12:14AM -0700, Ralph Campbell wrote:
>
> On 5/7/19 6:15 AM, Souptick Joarder wrote:
> > On Tue, May 7, 2019 at 5:00 AM <rcampbell@nvidia.com> wrote:
> > >
> > > From: Ralph Campbell <rcampbell@nvidia.com>
> > >
> > > The helper function hmm_vma_fault() calls hmm_range_register() but is
> > > missing a call to hmm_range_unregister() in one of the error paths.
> > > This leads to a reference count leak and ultimately a memory leak on
> > > struct hmm.
> > >
> > > Always call hmm_range_unregister() if hmm_range_register() succeeded.
> >
> > How about * Call hmm_range_unregister() in error path if
> > hmm_range_register() succeeded* ?
>
> Sure, sounds good.
> I'll include that in v2.
NAK for the patch see below why
>
> > >
> > > Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
> > > Cc: John Hubbard <jhubbard@nvidia.com>
> > > Cc: Ira Weiny <ira.weiny@intel.com>
> > > Cc: Dan Williams <dan.j.williams@intel.com>
> > > Cc: Arnd Bergmann <arnd@arndb.de>
> > > Cc: Balbir Singh <bsingharora@gmail.com>
> > > Cc: Dan Carpenter <dan.carpenter@oracle.com>
> > > Cc: Matthew Wilcox <willy@infradead.org>
> > > Cc: Souptick Joarder <jrdr.linux@gmail.com>
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > ---
> > > include/linux/hmm.h | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> > > index 35a429621e1e..fa0671d67269 100644
> > > --- a/include/linux/hmm.h
> > > +++ b/include/linux/hmm.h
> > > @@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
> > > return (int)ret;
> > >
> > > if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
> > > + hmm_range_unregister(range);
> > > /*
> > > * The mmap_sem was taken by driver we release it here and
> > > * returns -EAGAIN which correspond to mmap_sem have been
> > > @@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
> > >
> > > ret = hmm_range_fault(range, block);
> > > if (ret <= 0) {
> > > + hmm_range_unregister(range);
> >
> > what is the reason to moved it up ?
>
> I moved it up because the normal calling pattern is:
> down_read(&mm->mmap_sem)
> hmm_vma_fault()
> hmm_range_register()
> hmm_range_fault()
> hmm_range_unregister()
> up_read(&mm->mmap_sem)
>
> I don't think it is a bug to unlock mmap_sem and then unregister,
> it is just more consistent nesting.
So this is not the usage pattern with HMM usage pattern is:
hmm_range_register()
hmm_range_fault()
hmm_range_unregister()
The hmm_vma_fault() is gonne so this patch here break thing.
See https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-5.2-v3
next prev parent reply other threads:[~2019-05-12 15:07 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 23:29 [PATCH 0/5] mm/hmm: HMM documentation updates and code fixes rcampbell
2019-05-06 23:29 ` [PATCH 1/5] mm/hmm: Update HMM documentation rcampbell
2019-06-06 14:02 ` Jason Gunthorpe
2019-06-06 18:50 ` Ralph Campbell
2019-06-06 19:32 ` Jason Gunthorpe
2019-05-06 23:29 ` [PATCH 2/5] mm/hmm: Clean up some coding style and comments rcampbell
2019-06-06 14:16 ` Jason Gunthorpe
2019-06-06 14:27 ` Jerome Glisse
2019-06-06 15:41 ` Jason Gunthorpe
2019-06-06 15:52 ` Jerome Glisse
2019-06-06 16:55 ` Joe Perches
2019-06-06 18:54 ` Jason Gunthorpe
2019-06-06 15:57 ` Jason Gunthorpe
2019-06-07 0:44 ` Ralph Campbell
2019-05-06 23:29 ` [PATCH 3/5] mm/hmm: Use mm_get_hmm() in hmm_range_register() rcampbell
2019-05-23 12:51 ` Jason Gunthorpe
2019-05-23 18:19 ` Ralph Campbell
2019-05-23 18:46 ` John Hubbard
2019-05-06 23:29 ` [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() rcampbell
2019-05-07 13:15 ` Souptick Joarder
2019-05-07 18:12 ` Ralph Campbell
2019-05-09 4:42 ` Souptick Joarder
2019-05-12 15:07 ` Jerome Glisse [this message]
2019-05-12 15:28 ` Jerome Glisse
2019-05-13 17:23 ` Ralph Campbell
2019-06-06 14:50 ` Jason Gunthorpe
2019-06-06 19:44 ` Ralph Campbell
2019-06-06 19:54 ` Jason Gunthorpe
2019-06-06 21:08 ` Ralph Campbell
2019-05-12 15:08 ` [PATCH 0/5] mm/hmm: HMM documentation updates and code fixes Jerome Glisse
2019-05-13 17:26 ` Ralph Campbell
2019-05-13 18:10 ` Jerome Glisse
2019-06-06 14:53 ` Jason Gunthorpe
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